DBPapers
DOI: 10.5593/SGEM2016/HB63/S08.039

OPTIMISATION OF PRETREATMENT CONDITIONS OF PLANT RAW MATERIALS COMPOSED MEDIA FOR CAROTENOID BIOSYNTHESIS BY YEAST RHODOTORULA RUBRA

B.A. Karetkin, O.P. Chervyakova, D.V. Baurin, I.V. Shakir, V.I. Panfilov
Friday 11 November 2016

References: 16th International Multidisciplinary Scientific GeoConference SGEM 2016, SGEM Vienna GREEN Extended Scientific Sessions, www.sgemviennagreen.org, SGEM2016 Conference Proceedings, ISBN 978-619-7105-79-7 / ISSN 1314-2704, 2 - 5 November, 2016, Book 6 Vol. 3, 301-308pp, DOI: 10.5593/SGEM2016/HB63/S08.039

ABSTRACT
Various types of plant processing by-products (wheat bran, sunflower husk and meal, coffee sludge), as well as unconventional agricultural products (tubers of Jerusalem artichoke) were considered as a major component of culture media for Rhodotorula rubra submerged fermentation. β-Carotene, torulene and torularodin prevail among the other carotenoids of the strain investigated. The yeast biomass was extracted with petroleum ether and the concentration of the substances was determined by spectrophotometry for the analysis of the carotenoids. During plant raw materials processing, by-products concentrate fiber components, which yeasts do not use. Therefore, these components were processed with cellululase (Cellic CTec2, Novozyme) and hemicellulase (Cellic HTec2, Novozyme) containing enzymes and also with balanced blend Viscoferm (Novozyme). Sulfuric acid hydrolysis was studied as an alternative pretreatment method. Jerusalem artichoke fructans were metabolized without additional hydrolysis. Solvent:solid ratio was 12:1 for Jerusalem artichoke, and 10:1 for other plant materials. The maximal yields of the reducing substances (52.3 g/L) and total carbohydrates (65.4 g/L) were obtained after the dilute acid hydrolysis of the Jerusalem artichoke.
Submerged aerobic fermentation of yeasts was carried out in Erlenmeyer flasks at 30 °C and stirred (150 min-1). The count of cells was determined in a counting chamber. Final concentrations of yeasts after fermentation on the water extracts of Jerusalem artichoke tubers constituted 14 g/L, and it did not exceed 10 g/L in the other cases. At the same time accumulation of the carotenoids in biomass constituted up to 44.2 μg/L, which corresponded 282.6 μg/L of culture media after tubers acid hydrolysis. Despite the amount of carotenoids in yeast obtained on fluid extracts of Jerusalem artichoke was significantly lower due to a high cell titer, the concentration of carotenoids in culture medium reached 278.2 g/L. On the next stage of our research Jerusalem artichoke tubers pretreatment conditions of the were optimized using central compositional design. The following conditions of hydrolysis were chosen for pH, temperature and duration of treatment: center points – 2.5, 120.0 °С and 25 min, variation interval for a full factorial design – 1.25, 6 °С and 10 min. Star points level was 1.682. The response surface were obtained for reducing substances, final yeast yield and carotenoids concentration. The hydrolysis conditions of Jerusalem artichoke tubers were investigated and optimized including reducing substances yield. The optimal values of hydrolysis parameters were
pH 1.24, temperature 110.6 °С, duration of hydrolysis 25 min to maximal reducing
substances yield. Carotenoids yield reached its maximum at pH 1.59, temperature
107.0 °С, or pH 3.41 and temperature 114.0 °С and hydrolysis duration 25 min.
Predicated concentration of carotenoids in culture media being 392 μg/L for both
options was confirmed by the experimental data.

Keywords: carotenoids, Rhodotorula rubra, plant raw materials, central compositional
design, optimization

PAPER DOI: 10.5593/SGEM2016/HB63/S08.039, OPTIMISATION OF PRETREATMENT CONDITIONS OF PLANT RAW MATERIALS COMPOSED MEDIA FOR CAROTENOID BIOSYNTHESIS BY YEAST RHODOTORULA RUBRA

35 EURO ADD TO CART


Your cart ( items)

Subtotal:
Tax cost ():
Shipping cost:
Total:
Checkout Empty